Method and apparatus for melting oxids, &amp;c., without contamination



E. F. NORTHRUP.

METHOD AND APPARATUS FOR MELTTNG oxlns, 8m., w|THOuT CONTAMINATION.

APPLICATION P|Ln1uLY3o.1919. .l

Patented May 17, 1921.

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E. F. NORTHRUP.

METHOD AND APPARATUS FOR MELTING OXIDS, &c., WITHOUT CONTAMINATION.

APPLICATION FILI-:D IuLYso. 1919.

1,378, 1189.l Patented May 17, 1921.

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UNITED STATES PATENT orifice.

EDWIN FITCH NOBTHBUP, 0F PRINCETON, NEW ASSIGNOR, BY IBN! ASSIGNmTS, TO AJAX ELEC'.IlBOTIEIIERIIIIIC CORPORATION, OF TBENTON, NEW JERSEY, CORPORATION OF NEW JERSEY.

IETHOD AND APPARATUS POB HELTING OXIDS, Q0., WITHOUT CONTAIINATION.

Specication of Letters Patent.

Patented May 17, 1921.

Application Med July 30, 1919. Serial No. 314,241..

T o all ywlmm it may concern.'

Be it known that I, EDWIN F. NoR'rHnUr, a citizen of the United States, residing at 30 Wiggins street, Princeton, Vin the county of Mercer and State of New Jerse have invented a certain new and useful ethod andA Apparatus for Melting Oxids, &c., without Contamination, of which the following is a specification.

My` invention relates to electric furnaces and allied apparatus and appliances used 1n high temperature melting and heat treatment.

The purpose of my invention is to provlde for melting metallic oxids or other materials subject to contamination in such a manner as to prevent contact with any contaminating material during the melting.

A further purpose is to form a carbid coating upon the surface of a graphite crucible by union at high temperature between the graphite upon the crucible surface and a metal yielding coating.

A further purpose'is to melt a metallic oxid floated upon the surface of a molten pool of metal, preferably its own metal, by 'heat generated in the pool in the oxld or in the container.

A further purpose is to form a'protective side wall coating for a lighter content being melted 'or heat-treated, by spreading a liquid (here molten) content about the side -wall by centrifugal action.

A further purpose is to melt down a furnace content as a continuing operation, feeding the material in at the/top, heating it there by electrically induced current, concent-rating the current in the lower part, preferably by reducing the cross section there of the material within which the heat is developed or to which it is applied, and passing the molten material throughas it becomes melted, at all times protecting from contamination of the material by the surfaces with which it engages.

Further purposes will appear in the specification and in the claims.

My invention relates to the methods dis-4 closed and to apparatus by' which the processes may be carried out.'

I have preferred to illustrate my inven- 'may appear, selectin tion by a few only o-f the forms in which it different forms to ilustrate different app ications of my inventlon without attempting completeness of illustration and recognizing that many other varieties of my invention may be desi ed readily with the information contained herein.

Figures 1 and 2 are vertical longitudinal sections of a crucible embodying one form of my invention. V

Figs. 3, 4 and 5 are central vertical sections illustrating three other constructions contents. The latter, for examp e, may be a metallic oxid which is a non-conductor of electricity and has a high melting point. In such a case an electrically conducting crucible is used.

However', the higher the temperature to be attained the fewer the materials of any character which areA available for crucible use. Graphit-e, the best electrically-conducting crucible materials at any electric furnace temperature and particularly suitable for very "hi h temperatures and for the larger crucibgles, has a reducing action upon the oxids. Other materials, susceptible to contamination by the crucible for whatever reason, require protection from contact with it.

My present inventionyis directed to the methods and means for handling materials to be melted while protecting from contaminating influences. A

Because-the vmelting of oxids ha'sA presented great' diiculty on account of the high temperature usually r uired and these oxlds, most conveniently me ted in graphite 1,328,336 issued J anua crucibles, when melted by existing commercial methods have been changed by reduction to their metals throu h the action of carbon upon them, Irhave se ected for my first illustration, (Figs. 1 and 2) a method and graphite crucible protecting the contents from contamination.

The graphite crucible 7 is painted or otherwise covered with an oxid of a metal whose carbid it is desired to form upon the face coated. I.have shown the coating as internal only as it will ordinarily not be necessary to coat the outside; but the invention is not so restricted. An oxid which can be used to advantage is that of aluminum which may be painted u on the surface intended to be rendered sa e -from contamination.

Whatever the material used, after the surface has been covered with a layer of this material as at 8 the crucible is heated to a high temperature, preferably by a high frequency induction coil, of which examples are shown in my patents above and of which the best form is seen in my Patent No. 20, 1920. The oxid coating is reduced lat t e high temperature and the metal thus freed forms a carbid with the graphite of the crucible, as seen at 9.

The oxids of aluminum, boron, thorium and magnesium, magesium chlorid and the salts of iridium, osmiuin and platinum are 'ven by wayr of su gestion of the variety of initial coatings w ich may be used and, fused, have no reducing effect upon the melt.

Any of these and other materials, within the easy selection of the chemist in view of my disclosure, form upon the walls of the graphite container a coherent, intimate, strong coating of. carbid margin v into the graphite and capable of withstan in a very ig temperature. With other cruci les intended to have their contents protected against 'different kinds of contamination other forms of coating could be used.

This supplies a trustworthy crucible capable of general hi h temperature use but particularly suited or use in connection with a high frequency electric induction furnace (because vi-t is a conductor of electricity) and in which the is chemically united with the container and not a mere coating thereon. Taking u next the form of the invention shown in 1g. 3 I form a crucible out of a molded xid 1o, Lach as am oxid of thorium,

titanium, vanadium or zirconium-having a melting vpoint in excess of that of the melt 11, here for lconvenience referred'to' as an oxid. The 'oxid 11 preferably melted b means of shigh frequency, artificially cooled; inductor system such asmsshown vin my aplication for ,patent for 'artificially-cooled igh'. frequency coil, Serial No. 291,161, filed April,1 8, 1919,v water-'cooled coil 12 .about a supporting quartz tube 13 resting fused oxid' from a hopper 29.

upon a base 15. The oxid 11 is more readily' is more convenient and simplifies connec-4 tions.

Within the cylinder is shown a refractory heat insulator 16, surrounding a preferably molded 'non-conducting refracto 17 open at the center at the to and 18 and aving the opening relatively en arged or counterbored to provide a cavity 19 within which the melting is to take place.

, n order to protect the material to be melted, here exemplified as an oxid 11', from contamination by the walls of the refractory 17 I rovide a protective coating 20 of molten meta I which will not contaminate, (ordinarily the same metal as that in the oxid) and spread it over the walls of the cavity by centrifu al action upon a s aft 21 in ed bearings 22 and rotating the shaft, base and supported parts by pulley 23 and belt 24. Some one of the parts within the refractory 16 must be electrically conducting. This may be the molten metal, the oxid to be melted or even the refractory 17.

The metal may be spread over the surface of the cavi-ty before the oxid is inserted, or may be relied upon to take and maintain this position afterward in view of its greater ly mounting the base 15" specific gravity than that of the oxid. lVhere the molten metal is not that whose oxid is being melted it should have a hi her boiling point than the boiling point of t e oxid.

In Fig. 5 a Continuously operative form is shown .-in which an outer cylinder 132, which may be quartz, is given different diameters at 25 and `26 to receive artificially cooled high fr uenc coils 122, 123. These may be energize by t e same high frequency single phase supply or, conveniently by different phases o the saine supply. For different connections by which the single phase and two phase high frequenc current ma f be produced and a plied re erence is ma e to my patents an applications above mentioned.

A ver? thin funnel-shaped crucible 27 of a hi h using metal such as iridium or of grap ite-which in that case would be preared by a carbid liningis heat-insulated rom the cylinder, as by purest zirconia. sand 28, and receives a continuous su ply of unhe induced current heats' the oxid to a high temperature and, with the greater concentration within the smaller cross section at the bottom ture of the melt and a molten body (neck1 of the crucible it may be adjusted to fuse t upper part of the Crucible; providing for a continuous progression of the oxid downwardly and the delivery of molten oxid free from contamination in a'continuous stream through an openin 30 in a support 3() into a crucible 31 of mo ded oxid.

The induced current` may be further intensiied in'the lower part of the Crucible by increasing the turns of the coil or by other means polnted out by me in my patents and ap lication.

n all of these forms the oxid or other material is melted in aspecial crucible o r one having a specially prepared lining free from contaminating effect upon the oxid and preferably by a current induced in the oxid or in the crucible.'

Having thus described by invention, what I claim as new and desire to secure by Letters Patent is 1. In the melting of metallic oxids and like chemicals the combination of a crucible composed of agnetallic oxid having a melting point in excess of the intended temperaof the metal whose oxid is being treated within the bottom of the Crucible.

2. In the melting of metallic oxids and like chemicals, the combination of a crucible composed of a metallic oxid having a melting point in excess ofthe intended temperature of the melt anda body of the metal whose oxid is being treated, within the crucible.

3. A molded crucible for melting oxids,

etc., formed ofa high melting oxid in comhaving a high melting point and a molten pop therein of the same metal as that of the 0x1 v 5. A Crucible comprising a molded nietallic oxid having a high melting oint in com bination with a coll surroun ing the crucible, a high frequency source of current and connections for applying the current to the coil. f

6. In an electric furnace for melting oxids/etc., a non-reducing Crucible, an elecmelting point as high as that of the oxid, a source of high frequency electric Current and connections for applying the current inductivelyabout the pool.

7. In an electric furnace, an inductor coil, a support therefor, a source of high freuency current, connections for a plying t e current to the coil, a crucible wit in the e oxid there and not fuse that in the trically conducting pool therein having asupport, comprising a metallic oxid of higher melting point than the material intended to be melted therein and a fluid rcsistor in the crucible of higher melting point and s eciiic gravity than the intended melt.

8. crucible o'f electrically conducting material in combination with a carbid coating for said Crucible.

9. A. graphite crucible in combination with a carbid lining intimatelyv associated therewith.

10. A crucible in combination with a carbid lininv merging thereinto and chemically formed t ereon. l 11. A crucible of electrically conducting material having a lining intimately connected with it Comprising a carbid of the material of the crucible.

. 12. A crucible having a carbid lining blending into the material of the crucible.

13. A graphite Crucible in combination with a non-silicious, non-reducing lining rigidly Connected therewith.

14. An electric furnace comprising an inductor coil, a`source of hi h frequency Current, connections for app ying the current to the coil, a rotatable Crucible within the coil and means for rotating the crucible while it is being acted upon by the Coil.

15. An electric furnace comprising a stationary inductor coil, Connections for applying the current to the coil, a rotatable crucible within the coil'and means for rotating the crucible while it is being acted upon :by the coil.

16. An electric furnace comprising an inductor coil, a source of high frequency current, connections for applying the current to the Coil, a rotatable crucible within the coil havingan enlarged central bore and means 105 for rotating the Crucible 'while it is being acted Vupon by the coil.

1'7. An electric furnace com rising an inductor coil, a source of hi h requency current, connections for app ying the -current 110 to the coil, a rotatable crucible within the field of the coil andhaving an enlarged bore and means for rotating the crucible while it is being acted upon by the"coil.

18. An electric furnace com rising an in- 115 ductor coil, a source of high requency current, connections forapplying the current to thecoil, a rotatable Icrucible within the coil of nonreducing material, means for rotating'the Crucible Vwhile it is being acted 120 upon by the Coil and a molten nonreducing charge therein different from the melt.

19. An electric-furnace comprising a crucible having tapering cross section smaller at the bottom 1n combination with a high 125 frequency inductor surrounding the crucible and concentrating inductive effect more greatly upon the lower portion than upon the up r rtion.

20. n induction furnace, comprising 180 upper and lower communicating tapering furnace sections in combination withseparate inductor coils therefor and electric current supply of different phase for the two4 coils.

linmg, supporting the lining, an indctor 'coil surrounding the .casing and high freuen current supply for 4the coil. q method of forming a linin for a crucible, which consists in coatin t e crucible with a metallic compoun capable of reduction by heat, such as an oxid of aluminum or a chlorid of a vmetal of the platinum group, and heating it to a high temperature to cause reduction of the metallic compoundand'combination of the metal to transform a lining thereto so that it shall from reduction-while melting it, which con- 27.Inthe the recess, which consists in coating'thez therefrom with the 'material of the crucible.

24. The method of protectin a melt from.

contamination 'from a grap nite crucible, which consists in coating thecrucible with a reducible metallic oxid or chlorid and in heating the crucible to cause reduction of the coating and combination of the metal thus freed with the phite of the crucible.

25. The method o lining a crucible hsva reducing action upon the material contamed,pto protect against this reducing action, which consists in coating the crucible with a material capable ofbeing reduced by the reducing action of the crucible and of chemically combining' with the crucible when so reduced and subsequently heating the crucible so coated to bring about the reduction and-recombination.

26. The method of lining a crucible comof material deleterious to certain intended contents, which consists in utilizing the deleterious characteristic of the crucible recombine with the material of the crucible to protect against further deleterious action.

protection against contamination of the content of the crucible of electric furnaces upon substance withinthe crucible,

` cruclle with a'material subject to the same character of contamination and heating the crucible to cause the contaminating action of oxid in contact with nonreduc' molten body of the metal of oxid to be melted.

29. The method of melting an oxid free from reduction, which consists inmelting the oxid in a" nonreduc' crucible in'the esence of the metal ofw 'ch it is an oxid y current induced in the oxid or the metal beneath it.

30. The method of protecting a material -being treated from contact with the walls of the vessel in which the treatment is taking glace, which consists in providing4 a li ui or molten content within the vessel; w ich content is heavier than the material being'treated and in whirling thel vessel durf ing the treatment to spread the heavier contentbetween the material treated-and the.

walls of the vessel while takinglpllace. 31. e method of -p from contamination by contact with'the cru cible within which it is being melted which consists in providing a pool of molten metal beneath the oxid in the crucible and whirling the crucible while the oxid .is being the ltreatment is melted to distribute the -metal about the walls of the crucible. A

32. The' method of protect' an oxid from contamination by contact with the crucible within which it 1s being melted which consists in fprovidin a pool of molten metal like that o the oxi beneath .the oxid in the crucible and whirling the crucible while th'e oxidis being melted to distribute the metal about the walls of the crucible.

33. The method of protecting an oxid from contamination by; contact with thei crucible within which it is be' melted which consists in maintaining a yer of protective molten metal between'` the oxid and the wall of the crucible.

34. The method of. protecting an oxid sists in constantly pro ing the oxid from a region of relatively arge cross section and low temperature throug legions of small cross section and high temperature until the oxid is molten and melted into a mold while main the aces.

EDWIN FITCH N0 UP.

an oxid ausl raining the oxid as it is 

